Recently, man-machine interfaces in usage of touch modules are more user-friendly and become more and more popular. Therefore, the man-machine interfaces in usage of the touch modules are widely applied to electronic products. Generally, the touch modules include resistance touch modules, capacitive touch modules and optical touch modules, wherein the optical touch modules have an advantage of lower cost.
FIG. 1 is a schematic view of a conventional optical touch module. Referring to FIG. 1, the optical touch module 100 includes a light guide assembly 110, a light emitting device 120 and a light sensing device 130. The light guide assembly 110 includes a pair of light guide bars 112a, 112b, and a strip mirror 114. The pair of light guide bars 112a, 112b and the strip mirror 114 are arranged on three side of a rectangular track, wherein the light guide bar 112a is opposite to the strip mirror 114, and the light guide bar 112b is connected between the light guide bar 112a and the strip mirror 114. The area surrounded by the rectangular track is a sensing area 116. Furthermore, the light emitting device 120 is disposed at the joint of the pair of light guide bars 112a, 112b and configured for emitting light to the light guide bars 112a, 112b. The light guide bars 112a, 112b are configured for converting the light from the light emitting device 120 into linear light, and the liner light illuminates the overall sensing area 116. Moreover, the light sensing device 130 is arranged beside the light guide bar 112a, and a Field of View (FOV) of the light sensing device 130 covers the entire sensing area 116.
The light sensing device 130 is configured for detecting whether there is any light shielding object in the sensing area 116 or not, and calculating the position of the light shielding object in the sensing area 116. In detail, the light sensing device 130 detects the dark points A2, A3 when a mirror point A1 of the touch point (e.g. light shielding object) A in the sensing area 116 is produced through the strip mirror 114. Therefore, the distances d1, d2 can be calculated, and thus the position (coordinates) of the touch point A1 can be calculated by using the distances d1, d2 and other known parameters. The other known parameters include the length of the sensing area 116 along the axis X, the width of the sensing area 116 along the axis Y, the shortest distance between the touch point A and the strip mirror 114 that is equal to the shortest distance between the mirror point A1 and the strip mirror 114, and so on. A detailed method of calculating coordinates is obvious to one of ordinary skill in the art, and thereby the detail description is omitted.
However, the conventional optical touch module 100 has a blind zone 150 formed in an area between the broken line 151 and the strip mirror 114. That is to say, the blind zone 150 is an area which is unable to accurately calculate the position of the touch point. For example, when the touch point B in the sensing area 116 is located in the blind zone 150, the dark point B2 caused by the touch point B and the dark point B3 caused by the corresponding mirror point B1 are partially overlapped, and thereby the position (coordinates) of the touch point B cannot be accurately calculated.